Wire grid polarizer and method of manufacture

ABSTRACT

A polarizing optical article formed by selectively applying a conductive coating to a portion of a structured surface formed of a series of linear peaks and valleys.

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/616,578 filed Feb. 6, 2015 entitled Wire GridPolarizer And Method Of Manufacture (issuing as U.S. Pat. 10,101,515 onOct. 16, 2018), which claims priority to U.S. Provisional ApplicationSer. No. 61/936,831 filed Feb. 6, 2014, entitled Wire Grid Polarizer andMethod of Manufacture, both of which are hereby incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

The present invention is directed to devices and methods ofmanufacturing devices for polarizing light and, more particularly,devices employing wire grid polarizers.

BACKGROUND OF THE INVENTION

Polarizing functionality for optical lenses is required to betransmissive by virtue of the application and is typically provided byuse of a stretched polyester or polyvinyl alcohol, PVA, film that issubsequently imbibed with a conductive material such as iodine orsuitable organic dye. Such stretched film polarizing sheets can have upto 99.9 percent polarizing efficiency. However, at such high levels ofefficiency, the optical transmission is typically reduced to a levelclose to 20 percent. The application space of ophthalmic lenses requiresthat the polarizing film material is entrained within the lens packageitself.

An alternative technology to stretched film is wire grid polarizers,WGP. Wire grid polarizers have typically only been used for relativelylong wavelength applications such as microwave, infrared, IR, and longerwavelengths because the wires available for employing in the polarizershave been too large to be effective to polarize the shorter wavelengths,such as wavelengths within the visible spectrum, e.g. approximates 390to 700 nanometers. In order to enable visible light polarization, thespacing of wires in a wire grid polarizers needs to be below thewavelength of visible light, and preferably significantly below thelowest wavelength, for example 200 nanometers.

Hence, there exist a need in the field for wire grid polarizers that areoperable to efficiently polarize the relatively shorter wavelengths inthe visible light spectrum.

OBJECTS AND SUMMARY OF THE INVENTION

The present invention provides wire grid polarizers that are operable toefficiently polarize the relatively shorter wavelengths in the visiblelight spectrum. These objectives are achieved, in part, by providing alens having a first and second surface through which a lens user looks,a substantially uniform linear series of peaks and valleys formed on oneof said first and second surfaces, and a conductive coating applied toless than an entirety of the series of peaks and valleys so as to form aseries of conductive wires across said one of said first and secondsurfaces of said lens. In certain embodiments, a substantially uniformlinear series of peaks and valleys is molded into one of said first andsecond surfaces. In certain embodiments, the conductive coating isapplied to only a portion of a tip of the peaks of the substantiallyuniform linear series of peaks and valleys.

The present invention also provides methods for making wire gridpolarizers that are operable to efficiently polarize relatively shorterwavelengths in the visible light spectrum. The method includes, in part,the steps of forming a linear structured surface on an optical articleand coating less than an entirety of the linear structured surface witha conductive coating so as to form substantially distinct individualwires on the optical article.

Alternatively, methods according to the present invention include, inpart, forming a linear pattern of peaks and valleys on a surface of anophthalmic article and coating the surface of the ophthalmic articlewith a conductive coating from an angle relative to a best fit linethrough the surface of the ophthalmic article that is greater than zeroand less than 90 degrees; and forming a plurality of conductive wiresacross at least a portion of the surface of the ophthalmic articlethrough said coating.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which

FIG. 1 is a micrograph of a surface structure of an ophthalmic articleaccording to certain embodiments of the present invention.

FIG. 2 is a cross-section of a surface structure of an ophthalmicarticle according to certain embodiments of the present invention.

FIG. 3A is a plan view of an ophthalmic article according to certainembodiments of the present invention.

FIG. 3B is an elevation view of an ophthalmic article according tocertain embodiments of the present invention.

FIG. 4 is a perspective view of an ophthalmic article according tocertain embodiments of the present invention.

FIG. 5 is a perspective view of an ophthalmic article according tocertain embodiments of the present invention.

FIG. 6 is a plan view of a surface structure of an ophthalmic articleaccording to certain embodiments of the present invention.

FIG. 7 is a plan view of a surface structure of an ophthalmic articleaccording to certain embodiments of the present invention.

FIG. 8 is a cross-sectional view of a surface structure of an ophthalmicarticle according to certain embodiments of the present invention.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

Broadly speaking, the present invention achieves the formation of wiregrid polarizers that polarize electromagnetic radiation in a range ofwavelengths that is within the visible spectrum, e.g. approximately 390to 700 nanometers. This objective is achieved by first forming astructured surface on an ophthalmic or optical article, such as a lens,a film, or a film laminate. The structured surface may employ a systemof linear patterns or features, such as peaks and valleys, ranging inthe scale of nanometers to hundreds of nanometers.

While an optical article employing such a structured surface shows amoderate level of visible light polarization, polarization increasesgreatly by selectively coating the structured surface with a conductivecoating. The structured surface is selectively coated with a conductivelayer such that the structured surface of the optical article allows foronly certain portions of the structured surface of the article, forexample a portion of a side of the peaks or a portion of the tip of thepeaks, to receive the coating. The selectively coated portions of thestructured surface thereby form a series of linear wires on the surfaceof the optical article that function as a wire grid polarizer.

In certain embodiments of the present invention, the surface upon whichthe inventive wire grid polarizer is formed is a front or back surfaceof an unfinished, single or multifocal optical lens puck or a front orback surface of a finished, single or multifocal optical lens.

In certain embodiments of the present invention, the desired surfacestructure is formed on the optical article during the casting orinjection molding process. For example, a mold, such as a metal mold,employed during the lens formation process may have the desiredstructure formed on a surface upon which or against which the opticalarticle will be formed. The surface structure may be formed on the moldby, for example, machining the mold with a diamond machining tip. Byemploying a relatively coarse diamond tip, for example a tip with aradius of curvature of 5 micrometers and a 35 degree tip angle, astructure having a distance between the peaks of linear features orcuts, i.e. a pitch, in the range of micrometers, for example 3micrometers, can be formed. By employing a relatively fine diamond tip,for example a tip with a radius of curvature of 1 micrometer and a 25degree tip angle, a pitch in the range of hundreds of nanometers can beformed. According to certain embodiments of the present inventionsurface structure in the range of 150 to 1000 nanometers is achieved,preferably in the range of 150 to 700 nanometers is achieved, and morepreferably in the range of 150 to 200 nanometers is achieved. Suchmachined optical molds may be referred to as directly tuned metaloptical components.

When an optical article is formed in a mold cavity having a surfacestructure such as described above, the lens substrate, for example apolycarbonate resin, conforms to the structured surface of the mold.Hence, when the optical article is removed from the mold, the surface ofthe optical article that was formed upon the structured surface of themold will have a surface structure substantially identical to thesurface structure of the mold cavity or to a reciprocal structure of thesurface structure of the mold cavity.

For example, a molded polycarbonate lens fabricated at a moldingtemperature in the range of 250 to 350 degrees Celsius, for example 295degrees Celsius, in a metal mold having a linear patterned surfacestructure will surprisingly have a structured surface with a high degreeof fidelity with the structured surface of the mold in which it wasformed.

FIG. 1 is an image of a micrograph of a portion of an optical articlemolded in a metal mold cavity having a linear patterned surfacestructure. The linear pattern of the surface structure of the mold wasformed with a pitch of approximately 6 micrometers. As shown in FIG. 1,the surface of the optical article formed against the structured surfaceof this mold also has a linear patterned surface structure. FIG. 2 is asurface profile of a portion of the same structured surface of theoptical article that was formed against the structured surface of thisstructured surface mold.

In certain embodiments of the present invention, the desired surfacestructure is formed directly into a front or back surface of a finishedlens, non-finished lens, or blank lens puck. For example, the abovedisclosed diamond cutting technique may be employed for the directsurfacing or structuring of a surface of a formed lens or puck, e.g. apolycarbonate lens or puck.

FIGS. 3A and 3B are plan and elevation views, respectively, of afinished or semi-finished lens 10, according to certain embodiments ofthe present invention, having a front side 12 and a back side 14. Thelens 10 employs a surface structure 16 on the front surface 12 that wasformed either during the lens molding process or as a result of directsurfacing of the front side 12. For the sake of clarity, the linearfeatures of the surface structure 16 are shown as if magnified and arenot shown to scale relative to the actual dimensions of the lens.

In certain embodiments of the present invention, the desired surfacestructure is formed on a surface of a thin film or a thin film laminate,for example a functional laminate such as a photochromic laminate. Thestructured surface may, for example, be formed on the film or filmlaminate by ruling or other suitable techniques. The surface structuredfilm or film laminate can then be employed alone to form a polarizingoptical article having the inventive wire grid polarizer or can bemolded through injection molding or casting to form laminate lenses, forexample a single or multifocal ophthalmic lens. FIG. 4 shows a film 20according to certain embodiments of the present invention, having afront side 22 and a back side 24. The film 20 employs a surfacestructure 16 on the front surface 22 that was formed either duringformation of the film 20 or as a result of direct surfacing of the film20. For the sake of clarity, the linear features of the surfacestructure 16 are shown as if magnified and are not shown to scalerelative to the actual dimensions of the lens.

FIG. 5 shows a film laminate 30 according to certain embodiments of thepresent invention, having a front side 32 and a back side 34 andlaminated layers 38A, 38B, and 38C. The film laminate 30 employs asurface structure 16 on the front surface 32 that was formed eitherduring formation of the laminate layer 38A; as a result of directsurfacing of the laminate layer 38A, prior to formation of the filmlaminate 30; or as a result of the direct surfacing of the front side 32of film laminate, after formation of film laminate 30, i.e. as a resultof direct surfacing of the front side 32 after the formation process ofthe laminate 30 (e.g. surfacing or patterning the front side 32 in theform of a polycarbonate sheet). For the sake of clarity, the linearfeatures of the surface structure 16 are shown as if magnified and arenot shown to scale relative to the actual dimensions of the lens.

In certain embodiments of the present invention, the structured surfacethat will ultimately be employed to form the inventive wire gridpolarizer, employs a structured pattern that, once selectively coated asdescribed below, will have different regions that polarize light indifferent orientations. For example, as shown in FIG. 6, the surfacestructure 16 may employ linear structure in a first region 16A andlinear structure in a second region 16B that is oriented at a non-zerodegree angle 18 relative to the linear structure in the first region16A.

With reference to FIG. 7, in certain embodiments of the presentinvention, the structured surface that will ultimately be employed toform the inventive wire grid polarizer, employs a linear structuredpattern of concentric circles 16C. The polarization of the opticalarticle employing such a surface structure will have some directionalityassociated with it depending on which direction the wearer is lookingthrough the optical article. For example, if the concentric circles arecentered on a pupil of a user, looking straight ahead will have anaveraged polarization state of substantially zero, looking up or downwill be polarized substantially horizontally, and looking left or rightwill be polarized substantially vertically.

In certain embodiments of the present invention, the same or differentsurface structure patterns may be combined in a single, contiguousregion or may be employed in separate discontinuous structured regionson the surface of the optical article. Stated alternatively, in opticalarticle employing multiple polarizing regions according to the presentinvention, the different regions may be formed in disperse regions ofthe article and need not contact or abut one another.

In order to from the “wires” of the inventive wire grid polarizer, thestructured surface is selectively coated with a conductive layer orcoating. The conductive coating may be applied or coated by, forexample, employing spray or sputter coating/deposition techniques, e.g.physical vapor deposition.

The term “selective” is intended to mean that the final result of thecoating process results in only certain portions of the structuredsurface being coated. For example, only portions of the sides of thepeaks or tips of the peaks of the structured surface will ultimately becoated with the conducting layer. In effect, the selective coatingprocess forms a series of distinct or discrete wires at a spatialfrequency, pitch, or separation in the order of nanometers that iseffective at polarizing wavelengths in the visible light spectrum.

In certain embodiments of the present invention, the wires thus formedare distinct or discrete wires or substantially distinct or discretewires. Alternatively stated, due the imperfections in, for example, thestructuring process and/or the conductive coating process, theconductive wires formed may contact one or more adjacent wires onoccasion. Hence, the term “substantially distinct” is intended to meanthe majority of the linear dimension of the wires formed are independentof one another.

In certain embodiments, as shown in FIG. 8, selective coating ormetallization is achieved by spraying or applying coating 40 to aportion of a peak 6 of structured surface 16. The selective coating isachieved, for example, by applying the coating from a direction,indicated by arrow 46, which forms an angle 44 that is non-zero degreeand less than 90 degrees to a best fit line or plane 42 of thestructured surface 16. Application of the coating 40 from direction 46results in only a portion of the surface structure 16 being coated,because the undulating topography of the surface structure 16 blocks orshadows portions of the surface structure 16 from the direct line ofsight or coating of direction 46. Due to the linear nature of thesurface structure 16, the coating or coated areas 40 continuesubstantially the entire length of the linear structure 16, therebyforming substantially continuous conductive wires on the surfacestructure 16.

In certain embodiments of the present invention, once the lens has beenformed with a structured or patterned surface mold and the wiresgenerated, additional coatings, for example hard coatings and/oranti-reflective coatings, can be applied to the structured surface so asto embed the wire grid polarizer and provide physical and environmentalprotection for the polarizer.

In certain embodiments of the present invention, the reflectivity,transmission, and polarizing efficiency of the wire grid polarizeraccording to the present invention can be tuned or optimized bymanipulating the pitch of the peaks of the structured surface and theangle 44 employed to selectively form the coating 40.

In certain embodiments of the present invention, the inventive wire gridpolarizer forms a graded polarizer across a portion or all of an opticalarticle, film, or film laminate. For example, from the perspective of auser, from a top to a bottom of an optical article the inventive wiregrid polarizer may vary such that the upper portion of the lens has ahigher polarizing efficiency than a lower portion of the opticalarticle. This embodiment may be advantageous, for example, when a useris driving a vehicle. While viewing at a distance through the upperportion of the optical article there is a high degree of polarization.However, when viewing closer objects, for example digital readouts orLCD screens within the cockpit of the vehicle, through the lower portionof the optical article, there is little or no polarization thatinterferes with the viewing of such devices.

In certain embodiments of the present invention, the conducting coatingemployed to form the wire grid polarizer is a reflective metal-typecoating. For example, the reflective conductor layer or coating mayemploy conductive metals such as gold, aluminum, copper, niobium,chromium, tin, or similar metals. The conductive, reflective layer mayform part of a multilayer structure or a more complex coating such as anenhanced mirror or a low-e coating, for example a coating in whichsilver is buried in the middle of many other layers that serve toprotect the metal and also provide aesthetic features. In certainembodiments, an anti-reflective coating is applied over the conductive,reflective coating so as to decrease or eliminate the reflective natureof the conductive, reflective coating.

In certain embodiments of the present invention, the conducting coatingemployed to form the inventive wire grid polarizer is a non-reflectiveconductor layer. For example, the non-reflective conductor layer mayemploy a metal-containing suboxide, multilayer stacks ofmetal-containing suboxides, or metal layers embedded within oxide or suboxide layer stacks. The non-reflective conductive coating can be, forexample, in the form of a low-e coating in which a metal suboxide suchas chrome suboxide or nickel chrome suboxide is employed. Thenon-reflective conductive coating may be embedded in non-reflective orabsorptive outer layers to enhance the non-reflective characteristics.Alternatively, such non-reflective or absorptive outer layers may beoriented below, on top or both on top and below of the non-reflectiveconductive layer to yield different visual cosmetic effects.

In certain embodiments of the present invention, the conducting coatingemployed to form the inventive wire grid polarizer is a transparentconductive layer. For example, the transparent conductor layer orcoating may employ a transparent conductive coating or TCC. For examplethe transparent conductive coating may employ indium tin oxide or ITO,zinc aluminum oxide, or a carbon-based conductor such as graphene. Suchtransparent conductive layer allows for the formation of a relativelyhigh transmission polarizing optical articles. In certain embodiments, atransparent conductive oxide is combined with other dielectric layerswhich will enable optical effects such as mirroring, anti-reflecting,and/or filtering, to be achieved in combination with the polarizingeffect

In certain embodiments in which a film or film laminate employing theinventive wire grid polarizer is in turn employed to form an opticalarticle or laminate optical article such as a lens, from example throughinjection molding or casting, the wires formed on the film or filmlaminate will, but need not necessarily be, molded or cast internal ofthe optical article. Alternatively stated, with reference to FIGS. 4 and5, during the injection molding or casting process, the lens substratewill be molded or case directly against the surface 22 or the surface32. In certain embodiments in which injection molding is employed, theactual surface structure of the surface 22 or the surface 32 may beflattened or otherwise lessened during the molding process.

In one embodiment of the present invention the wire grid polarizer isformed by first coating an optical article, film, or film laminate witha conductive coating and then forming the wires of the wire gridpolarizer by removal of linear portions of the conductive coating by,for example direct surfacing of the conductive coated surface of theoptical article, film, or film laminate. In this embodiment, the methodfor producing the inventive wire grid polarizer is essentially theopposite of the method described above, i.e. the conductive coating isapplied to the substrate prior to the surface structuring of thesubstrate. In certain situations, this embodiment may be advantageous inthat the wires fabricated by the conductive coating are not subject tothe above described selective, directional coating. Accordingly,non-linear or divergent polarizers may more easily be fabricated.

Wire grid polarizers according to the present invention achieve a muchgreater polarization efficiency than the current dye and stretched filmtechnologies used in ophthalmic lenses today. The current technologieshave a limit of approximately 80 percent polarizing efficiency atapproximately 50 percent transmission and a limit of approximately 96percent polarizing efficiency at approximately 40 percent transmission.At 98 percent polarizing efficiency, currently used technologies arelimited to approximately 15 percent transmission. The wire gridpolarizers according to the present invention advantageously andsurprisingly improve upon the polarizing efficiency and transmission ofcurrent polarizing technologies. For example, wire grid polarizersaccording to the present invention achieve polarizing efficiencies ofgreater than 99 percent at approximately 50 percent light transmission.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A method for forming a polarized ophthalmicarticle comprising: forming a linear structured surface on a film;coating the linear structured surface with a conductive coating so as toform substantially distinct individual wires on said film; applying aliquid form of a lens substrate to said film; allowing said liquid formto harden so as to form a laminate polarized ophthalmic article.
 2. Themethod of claim 1 wherein the step of applying said liquid form of saidlens substrate to said film comprises an injection molding process. 3.The method of claim 1 wherein the step of applying said liquid form ofsaid lens substrate to said film comprises a casting process.
 4. Themethod of claim 1 wherein the step of forming a linear structuredsurface on said film comprises the process of imprinting by replicationfrom a mold.
 5. The method of claim 1 wherein the step of forming alinear structured surface on said film comprises forming a series ofpeaks and valleys having a pitch in a range of 150 to 300 nanometers. 6.The method of claim 1 wherein the step of coating the linear structuredsurface with a conductive coating so as to form substantially distinctindividual wires on said film comprises coating only a portion of a tipof a plurality of peaks of the linear structured surface.
 7. The methodof claim 1 wherein the step of coating the linear structured surfacewith a conductive coating so as to form substantially distinctindividual wires on said film comprises coating from an angle relativeto a best fit line through the surface of the optical article that isgreater than zero and less than 90 degrees.
 8. The method of claim 1wherein the step of coating the linear structured surface with aconductive coating so as to form substantially distinct individual wireson said film comprises coating a reflective conductive coating.
 9. Themethod of claim 1 wherein the step of coating the linear structuredsurface with a conductive coating so as to form substantially distinctindividual wires on said film comprises coating a non-reflectiveconductive coating.
 10. The method of claim 1 wherein the step ofcoating the linear structured surface with a conductive coating so as toform substantially distinct individual wires on said film comprisescoating a transparent conductive coating.
 11. A method for forming apolarized ophthalmic article comprising: forming a linear pattern ofpeaks and valleys on a surface of a film; coating the surface of thefilm with a conductive coating from an angle relative to a best fit linethrough the surface of the film that is greater than zero and less than90 degrees; forming a plurality of conductive wires across at least aportion of the surface of the film through said coating; applying aliquid form of a lens substrate to said film; allowing said liquid formto harden so as to form a polarized ophthalmic article.
 12. The methodof claim 11 wherein the step of applying said liquid form of a lenssubstrate to said film comprises the process of injection molding. 13.The method of claim 11 wherein the step of applying said liquid form ofa lens substrate to said film comprises the process of casting.
 14. Alaminate polarized ophthalmic lens comprising: a film having asubstantially uniform linear series of peaks and valleys formed on asurface of said film; and a conductive coating applied to the series ofpeaks and valleys so as to form a series of conductive wires on saidsurface of said film; said film fused to a lens substrate throughhardening of a liquid state of said substrate to a solid state of saidsubstrate.
 15. The lens of claim 14 wherein said hardening comprises thesolidifying of an injection molded lens substrate.
 16. The lens of claim14 wherein said hardening comprises the solidifying of a cast lenssubstrate.